A survey among $50$ Brilliant users indicated that $33$ of them use the website to practice math, $24$ to practice science, and $19$ to practice computer science. Moreover, $9$ people study both math and science, $12$ both math and computer science, and $13$ both science and computer science. Nobody admitted to studying no subjects.

How many survey participants use Brilliant to study all three subjects? Keep reading to find out, or jump straight to today's challenge for a tougher problem.